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This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...
Visible-light astronomy has existed as long as people have been looking up at the night sky, although it has since improved in its observational capabilities since the invention of the telescope, which is commonly credited to Hans Lippershey, a German-Dutch spectacle-maker, [1] although Galileo played a large role in the development and ...
ICRF – (astrophysics terminology) International Celestial Reference Frame, a coordinate system based on radio sources used to define the locations of objects in the sky; ICRS – (astrophysics terminology) International Celestial Reference System, a coordinate system based on Hipparcos observations used to define the locations of objects in ...
In optical astronomy, interferometry is used to combine signals from two or more telescopes to obtain measurements with higher resolution than could be obtained with either telescopes individually. This technique is the basis for astronomical interferometer arrays, which can make measurements of very small astronomical objects if the telescopes ...
The telescope diameters are quoted in terms of the Fried parameter (defined below). r 0 {\displaystyle r_{0}} is a commonly used measurement of the astronomical seeing at observatories. At visible wavelengths, r 0 {\displaystyle r_{0}} varies from 20 cm at the best locations to 5 cm at typical sea-level sites.
Illustration of the use of interferometry in the optical wavelength range to determine precise positions of stars. Courtesy NASA/JPL-Caltech. Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
At the shorter wavelengths used in infrared astronomy and optical astronomy it is more difficult to combine the light from separate telescopes, because the light must be kept coherent within a fraction of a wavelength over long optical paths, requiring very precise optics. Practical infrared and optical astronomical interferometers have only ...
Infrared astronomy is founded on the detection and analysis of infrared radiation, wavelengths longer than red light and outside the range of our vision. The infrared spectrum is useful for studying objects that are too cold to radiate visible light, such as planets, circumstellar disks or nebulae whose light is blocked by dust.